I don’t use the batch edit feature a ton, but I’m not seeing it here.
In the batch edit screen you can open the description boxes but there’s no way to set all of the boxes to the same value, that I know about. I think you just have to copy and paste as you scroll down the screen.
In the batch upload screen it’s easy to select a bunch of observations and set the description to the same value using the box on the left.
Both of these are for the web version, I’m not sure if batch edit is even an option in the apps.